JP2004131755A - Recycling method for using smoke dust as raw material for iron making - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recycling method by which smoke dust is utilized as the raw material for iron making without subjecting the same to reclaiming treatment, and the economically treatable smoke dust is used as the raw material for iron making. <P>SOLUTION: Smoke dust 10 produced on a refuse disposal stage is mixed with a prescribed amount of iron source 11 and a chloride A12, and the mixture is heated to ≥700°C. By the heating, nonferrous metal contained in the smoke dust 10 is converted into a chloride B, and is volatilized and removed from the smoke dust 10 to obtain the raw material 13 for iron making. Thus, the smoke dust 10 is utilized as the raw material 13 for iron making without subjecting the same to reclaiming treatment, and can economically be treated. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a recycling method for treating soot generated in a refuse treatment process (eg, incineration treatment, melting treatment, etc.) and making soot that can be used as an ironmaking raw material as an ironmaking raw material.
[0002]
[Prior art]
About 50 million tons of general waste is generated annually from homes and small business establishments, and most of the waste is incinerated in, for example, a refuse incinerator. Most of the soot (also referred to as primary fly ash) generated after this treatment has been landfilled after, for example, cement solidification, chemical treatment, and melt solidification. It is becoming increasingly difficult and becoming a social problem.
Therefore, in order to recycle and reduce the volume of this soot, many municipalities have introduced ash melting furnaces to treat soot and refuse incinerators without introducing ash melting furnaces. Is replaced with a gasification and melting furnace to treat waste and to effectively use the generated molten slag. The produced slag is used, for example, for earth and wood such as backfill materials and roadbed materials, and fine aggregate for concrete products.
[0003]
[Problems to be solved by the invention]
However, in the ash melting furnace and the gasification melting furnace, molten slag is generated, and fly ash (also referred to as secondary fly ash or molten fly ash) in which repellent substances of the molten slag are concentrated is also generated. Since this fly ash is a concentrate of repellent substances, there is a concern about environmental pollution due to elution of heavy metals in the fly ash when landfilled.
However, when performing the treatment for preventing elution of heavy metals in the fly ash, a large processing cost is required and it is not economical. Even if the fly ash is subjected to some kind of pretreatment to prevent the elution of heavy metals after landfill disposal, heavy metals with a high environmental load will still accumulate in the landfill site, and long-term Does not solve the problem.
The present invention has been made in view of the above circumstances, and provides a method of recycling soot that can be used economically as a steelmaking raw material by using soot as a raw material for ironmaking without landfill disposal. The purpose is to:
[0004]
[Means for Solving the Problems]
According to the present invention, there is provided a method for recycling soot to be used as a raw material for ironmaking, comprising mixing a predetermined amount of an iron source and chloride A with soot generated in a refuse treatment step to 700 ° C. or more. By heating, the non-ferrous metal contained in the soot is converted into chloride B and volatilized and removed from the soot to obtain a steelmaking raw material. Here, the refuse treatment step means a step of performing a refuse incineration process or a melting process. Further, as the soot, for example, heavy metal-containing waste, municipal waste, industrial waste and the like, a powdery substance generated when incineration or melting treatment in the waste treatment process, for example, Primary fly ash, secondary fly ash and the like can be mentioned. The primary fly ash is a residue generated when waste is incinerated in a refuse incinerator (for example, smoke in exhaust gas). Secondary fly ash is generated in the process of turning residues generated during incineration or melting of refuse into slag, and repellent substances (for example, chromium (Cr), cadmium (Cd), arsenic ( As), selenium (Se), lead (Pb), mercury (Hg), etc.). Note that, as the iron source, for example, blast furnace dust, converter dust, and the like can be used, and as the chloride A, for example, calcium chloride and the like can be used. The obtained ironmaking raw material can be used, for example, as an iron raw material for a blast furnace, a converter, an electric furnace or the like in an ironmaking process.
As described above, by mixing the iron source and the chloride A with the soot and heating the mixture to 700 ° C. or higher, a conventionally known chloride volatilization reaction, that is, the oxide of a non-ferrous metal reacts with the chloride A, The reaction of volatilizing the metal chloride B proceeds. This allows the iron component in the iron source to remain, and removes the non-ferrous metal from the soot to obtain an iron making raw material, so that the soot can be used as an iron making raw material without landfill treatment.
[0005]
Here, in the recycling method for using soot as an iron-making raw material according to the present invention, the non-ferrous metal is preferably at least one of copper, lead, and zinc. Since the recovered non-ferrous metal is a useful metal, the recovered non-ferrous metal can be used as a raw material for non-ferrous refining.
In the recycling method according to the present invention for using soot as a raw material for ironmaking, soot is added to water or an acidic aqueous solution before being mixed with the iron source and the chloride A, and the alkali metal in the soot is added. It is preferable that chloride C is eluted and removed. Here, examples of the alkali metal chloride C in the smoke include calcium chloride (CaCl ₂ ), sodium chloride (NaCl), potassium chloride (KCl), and the like. As described above, since the alkali metal chloride C can be removed from the soot in advance, it is possible to prevent a furnace trouble caused by, for example, sodium chloride or the like.
In the recycling method according to the present invention for converting soot into iron raw material, heating of the mixture of soot, iron source and chloride A is performed in an oxidizing atmosphere to suppress volatilization of iron in the iron source. Is preferred. By heating the mixture of the soot, the iron source, and the chloride A in an oxidizing atmosphere, the iron component in the iron source is unlikely to be converted into chloride, and thus the non-ferrous metal chloride B is volatilized. Can be.
[0006]
In the recycling method according to the present invention for converting soot into ironmaking raw material, the amount of iron in the iron source mixed with soot is preferably 30% by mass or more of the total weight of the ironmaking raw material. Thereby, the obtained steelmaking raw material can have the necessary strength as a raw material to be charged into the blast furnace.
In the recycling method for using soot according to the present invention as an ironmaking raw material, iron oxide-containing dust discharged from an ironworks is used as an iron source, and a mixture of soot and iron oxide-containing dust is baked. It is preferable to remove carbon and then to mix chloride A. Since iron oxide-containing dust can be used as the iron source, the cost of the iron source can be reduced. In addition, since carbon can be removed by baking a mixture of soot and iron oxide-containing dust, for example, when a mixture of soot, iron source and chloride A is heated in a spherical shape, carbon is caused. Powdering of the spherical mixture can be prevented.
[0007]
In the recycling method according to the present invention for using soot as a raw material for ironmaking, it is preferable that the soot is molten fly ash generated in a step of turning a residue generated during incineration of refuse into slag. Thereby, the processing of the molten fly ash, which has conventionally been a problem of recycling, can be performed.
In the recycling method for using soot according to the present invention as a raw material for ironmaking, it is preferable to use the raw material for ironmaking as a raw material for blast furnace. Thereby, the iron raw material used in the blast furnace can be obtained at low cost.
In the recycling method for using soot as a raw material for ironmaking according to the present invention, it is preferable to use the raw material for ironmaking as an aggregate of concrete. Here, examples of the concrete include various concretes such as asphalt concrete and cement concrete. The obtained ironmaking raw material has sufficient strength as an aggregate for concrete and, since heavy metals are removed, can be used as an aggregate for various types of concrete.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention.
Here, FIG. 1 is an explanatory view of a chlorination and volatilization step of a recycling method for using soot as an iron-making raw material according to an embodiment of the present invention, and FIG. 2 is a leaching step and decarburization of the recycling method. FIG. 3 is an explanatory view of a granulation step of the recycling method, and FIG. 4 is an explanatory view of a heavy metal recovery step of the recycling method.
[0009]
As shown in FIG. 1 to FIG. 4, a method for recycling soot into ironmaking raw material according to one embodiment of the present invention includes a leaching step, a decarburizing step, a granulating step, a chloride volatilizing step, and In these processes, a predetermined amount of iron oxide-containing dust (an example of an iron source) 11 (for example, the amount of iron in the iron oxide-containing dust 11) is added to the soot 10 generated in the waste treatment process. However, iron oxide-containing dust 11 in an amount of 30% by mass or more (50 to 60% by mass in this embodiment) of the total weight of the finally obtained blast furnace raw material (an example of ironmaking raw material) 13 and calcium chloride (Example of chloride A) 12 was mixed and heated to 700 ° C. or higher, and by this heating, the non-ferrous metal contained in the mixture was converted into chloride B and volatilized and removed from the soot 10, and the blast furnace raw material 13 was used. Is a way to get The details will be described below.
[0010]
The soot 10 is a powdery substance that is generated when, for example, waste such as heavy metal-containing waste, municipal waste, industrial waste, or the like is incinerated or melted in the waste disposal process. Ash, secondary fly ash (also called molten fly ash), and the like.
Here, the heavy metal-containing waste includes heavy metal contaminated soil, organic matter contaminated soil, activated sludge, cement residue discharged from a ready-mixed concrete manufacturing plant, and the like. The quality of fly ash in municipal solid waste incineration plants and industrial waste incineration plants varies greatly. For example, calcium (Ca): 30%, sodium (Na): 20%, and chlorine (Cl): 10%. And non-ferrous metals, iron (Fe), other heavy metals, and alumina (Al ₂ O) composed of one or more of copper (Cu), lead (Pb), and zinc (Zn). ₃ ), silica (SiO ₂ ) and the like are each contained in several percent.
[0011]
First, as shown in FIG. 2, the soot 10 is charged into an extraction tank 15 in which a liquid 14 made of water or an acidic aqueous solution (for example, water to which hydrochloric acid is added) is stored and stirred for a predetermined time. Thereby, the alkali metal chloride C, for example, calcium chloride, sodium chloride, potassium chloride, etc. contained in the soot 10 elutes into the liquid 14 and is removed from the soot 10. Here, when the liquid 14 is an acidic aqueous solution, heavy metals, calcium, and the like can also be eluted into the liquid 14 as a water-soluble substance and removed from the soot 10, and the load of chloride volatilization can be reduced. The amount can be reduced.
Next, by supplying the liquid 14 having the soot 10 to the filter press 16 and performing solid-liquid separation, the soot 10 from which the chloride C has been removed is subjected to a decarburization step, and the liquid in which the chloride C is dissolved 14 are sent to the heavy metal recovery step (the above is the leaching step).
[0012]
The soot 10 from which the chloride C has been removed is a dust 11 containing iron oxide discharged from an ironworks, for example, blast furnace dust containing iron oxide as a main component (for example, 40 to 50% by mass as iron, and lead as another component). , Zinc, sulfur, etc.), converter dust (eg, less than 60% by mass as iron, and zinc, calcium, etc. as other components about 10%), etc. It is put into the oxidizing furnace 17 and burned. As a result, the mixture A (a mixture of the soot 10 and the iron oxide-containing dust 11) from which the carbon component has been removed from the inside is subjected to the granulation step, and the components (eg, metals) in the exhaust gas generated at this time are recovered as heavy metals. Each is sent to the process.
[0013]
As described above, the amount of the iron oxide-containing dust 11 mixed with the soot 10 from which the chloride C has been removed depends on the amount of iron in the iron oxide-containing dust 11 as the total amount of the blast furnace raw material 13 finally obtained. It is preferable to add an amount of 30% by mass or more of the weight, but it is also possible to determine based on the iron amount required for the finally obtained blast furnace raw material 13. It is preferable that the content be 50% by mass or more of the total weight.
Here, when the amount of iron in the iron oxide-containing dust 11 is less than 30% by mass of the total weight of the finally obtained blast furnace raw material 13, the manufactured product cannot have the necessary strength as the blast furnace raw material 13. And cannot be used as a raw material. Therefore, in order to ensure that the manufactured product has a strength that can be used as the blast furnace raw material 13, the amount of iron in the iron oxide-containing dust 11 to be added should be 40% by mass or more of the total weight of the blast furnace raw material 13, and furthermore, 50%. It is preferable that the content be not less than mass% (the above is the decarburization step).
[0014]
The mixture A from which the chloride C was removed in the leaching step and the carbon was removed in the decarburization step was mixed with an aqueous solution of calcium chloride 12 as shown in FIG. Using 18, the particle size is granulated to, for example, 10 mm. Here, the amount of the added calcium chloride 12 is, for example, about two to three times the theoretical equivalent required for the reaction of the non-ferrous metal contained in the mixture A in consideration of the reaction efficiency.
The processed product 19 (also referred to as a raw ball) granulated by the pan pelletizer 18 is dried while being conveyed by a conveyor dryer 20 which is an example of a drying device, and then sent to a chlorinating and volatilizing step. The dried processed material 19 is also called a dry ball.
As described above, the soot 10 is put into the liquid 14 before being mixed with the iron oxide-containing dust 11 and the calcium chloride 12, and the sodium chloride in the soot 10 is eluted into the liquid 14 and Since it has been removed, troubles in the furnace operation due to sodium chloride can be avoided in a subsequent step (the above, the granulation step).
[0015]
The treated product 19 to which the calcium chloride 12 has been added in the granulation step is continuously charged into a furnace of a rotary kiln 21 (for example, having a length of about 30 m) as shown in FIG. In the embodiment, the material is heated at, for example, 800 to 1200 ° C. for about 2 hours to produce a blast furnace raw material (product pellet) 13 mainly composed of iron oxide (Fe ₂ O ₃ ) and having an iron grade of, for example, 50 to 60 mass%. You.
In the furnace of the rotary kiln 21, a conventionally known chlorination volatilization reaction, that is, an oxide (MO) of one or more of non-ferrous metals of copper, lead, and zinc, for example, copper oxide (CuO), lead oxide ( PbO), zinc oxide (ZnO), and the like react with calcium chloride (CaCl ₂ ) to produce calcium oxide (CaO), and the non-ferrous metal chloride B (MCl ₂ ), for example, copper chloride (Cu ₂ Cl) ₂ ), a reaction in which lead chloride (PbCl ₂ ), zinc chloride (ZnCl ₂ ) and the like volatilizes proceeds. At this time, since air is blown into the furnace to form an oxidizing atmosphere, iron in the iron oxide-containing dust 11 hardly turns into chloride, chloride B of a non-ferrous metal volatilizes, and the iron oxide-containing dust 11 The volatilization of iron inside is suppressed.
[0016]
Here, when the heating temperature in the furnace of the rotary kiln 21 is less than 700 ° C., the non-ferrous metal cannot be sufficiently converted into chloride B, and the amount of the non-ferrous metal contained in the manufactured blast furnace raw material 13 increases, It cannot be used as a raw material. Further, even if the non-ferrous metal is converted to chloride B, the chloride B cannot be sufficiently volatilized, and the amount of non-ferrous metal contained in the blast furnace raw material 13 also increases. become unable. Therefore, in order to provide good quality as the blast furnace raw material 13, the heating temperature in the furnace of the rotary kiln 21 is preferably set to 750 ° C or higher, more preferably 800 ° C or higher. On the other hand, if the heating temperature is high, the chloride B of the non-ferrous metal can be sufficiently volatilized. Therefore, the upper limit is not specified, but if the heating temperature is higher than the melting temperature of the mixture A, Volatilization is inhibited. Therefore, in order to volatilize the nonferrous metal chloride B, the heating temperature in the furnace of the rotary kiln 21 is preferably set to 1300 ° C. or lower, more preferably 1200 ° C. or lower.
[0017]
Exhausted heat discharged together with the blast furnace raw material 13 from the downstream side of the rotary kiln 21 is supplied into the furnace through a burner unit 22 for heating the furnace of the rotary kiln 21. The volatile gas 23 discharged from the upstream side of the rotary kiln 21 is sent to the cooling tower 24.
In the cooling tower 24, cooling water is sprayed on the sent volatile gas 23 to dissolve the volatilized non-ferrous metal chloride B in the liquid. The liquid in which the non-ferrous metal chloride B is dissolved is sent to the heavy metal recovery step. On the other hand, the undissolved components are sent to the washing tower 25, where, for example, HCl, SOx, dust and the like are removed therefrom, and then sent to the dioxin removing tower 26, where detoxification treatment is performed. Later, it is released to the atmosphere (the above is the chloride volatilization step).
[0018]
The liquid 14 in which the chloride C is dissolved from the leaching step and the liquid in which the chloride B is dissolved, which is sent from the chlorination and volatilization step, are first put into the neutralization tank 27. Then, lime 28 is charged into the neutralization tank 27 to adjust the pH to a value at which the non-ferrous metal precipitates and precipitates. Thus, the non-ferrous metal chloride B (MCl ₂ ) reacts with calcium hydroxide (Ca (OH) ₂ ), and the non-ferrous metal hydroxide (M (OH) ₂ ) and calcium chloride (CaCl ₂ ) Is generated. Since the non-ferrous metal hydroxide (for example, Pb (OH) ₂ , Zn (OH) _2, etc.) precipitates from the liquid, the non-ferrous metal is separated and recovered using the filter press 29 each time. The collected non-ferrous metals are reduced (Yamamoto reduction) at each smelter and reused as non-ferrous smelting raw materials. Among the non-ferrous metals, for example, copper is recovered as metallic copper (copper grade of about 70%) by a substitution method with iron, and is reduced to a high grade by a neutralization reaction.
When iron is recovered here, it can be used as the blast furnace raw material 13.
[0019]
In addition, by sending the liquid solid-liquid separated by the filter press 29 to a calcium chloride concentrating device 30 using hot air or the like, calcium chloride dissolved in the liquid in the leaching step can be recovered. In addition, since this calcium chloride can be used as the calcium chloride 12 used in the granulation process, it can be effectively utilized and is economical.
Further, it is preferable that the liquid separated into solid and liquid by the filter press 29 is subjected to detoxification treatment, for example, by adding sodium hydrosulfide to remove other heavy metals. Process).
From the above, for example, the process conventionally used in the steel industry, that is, the process of removing repellent substances such as copper, lead, and zinc from iron-making dust generated in the iron-making process, and regenerating the iron raw material, It can also be used for soot recycling. At this time, not only heavy metals such as copper, lead and zinc, but also chlorine and alkali metals can be recovered or removed from the soot, and the remaining components (for example, calcium, silicon, and aluminum) are burned in the blast furnace raw material production. It becomes a binder and is used as a slag-making agent in the blast furnace, and is effectively used as an auxiliary material in the iron making process. In addition, since the amount of molten fly ash generated is less than 1% of the iron production in Japan, most of the molten fly ash uses existing social capital by using this recycling method. It is economical because it can be processed.
[0020]
As described above, the present invention has been described with reference to one embodiment. However, the present invention is not limited to the configuration described in the above-described embodiment, and is described in the claims. Other embodiments and modifications that can be considered within the scope of the present invention are also included. For example, a case where a part or all of the above-described embodiments and modified examples are combined to constitute a recycling method for using soot of the present invention as a steelmaking raw material is also included in the scope of rights of the present invention.
In the above-described embodiment, iron oxide-containing dust is used as the iron source. However, other iron sources, for example, wastes such as sludge and sludge containing iron, can be used.
In the above-described embodiment, the case where the steelmaking raw material is used as the blast furnace raw material has been described. Is also possible.
[0021]
【The invention's effect】
In the recycling method for using soot as an iron-making raw material according to claims 1 to 9, the iron component in the iron source remains, and the non-ferrous metal is removed from the soot to obtain the iron-making raw material. It is possible to recycle the soot as a raw material for iron making and economically treat it without landfilling the soot.
In particular, in the recycling method for using soot as an iron-making raw material according to claim 2, since the recovered non-ferrous metal is a useful metal, the recovered non-ferrous metal can be used as a raw material for non-ferrous refining. In addition, resources can be effectively used. In the recycling method for converting soot into iron raw material according to the third aspect, since the alkali metal chloride C can be removed from the soot in advance, troubles in the furnace caused by, for example, sodium chloride and the like can be prevented beforehand. And stable operation is possible.
[0022]
In the method for recycling soot as an iron-making raw material according to claim 4, heating of the mixture of the soot, the iron source and the chloride A in an oxidizing atmosphere allows the iron component in the iron source to be heated. With the volatilization suppressed, the non-ferrous metal chloride B can be volatilized. As a result, the iron grade in the ironmaking raw material can be raised to a level that can be economically recovered.
In the recycling method for converting soot into ironmaking raw material according to claim 5, since the obtained ironmaking raw material has a necessary strength as a raw material to be charged into a blast furnace, for example, without further processing. It can be used as a raw material for steelmaking.
[0023]
In the method for recycling soot as an iron-making raw material according to claim 6, since iron oxide-containing dust can be used as the iron source, the cost of the iron source can be reduced and it is economical. Further, by burning a mixture of soot and iron oxide-containing dust, carbon in the soot can be removed. For example, when a mixture of soot and iron source and chloride A is heated in a spherical shape, carbon is removed. Can prevent the spherical mixture from being powdered, and can perform the operation safely.
In the method for recycling soot as an iron-making raw material according to the seventh aspect, it is possible to economically perform the processing of molten fly ash, which has conventionally been a problem of recycling.
In the recycling method for using dust as an iron-making raw material according to claim 8, since the iron-making raw material is used as the blast furnace raw material, the iron raw material used in the blast furnace can be obtained at low cost and is economical.
In the recycling method for converting soot into iron raw material according to claim 9, since the obtained iron raw material has sufficient strength as an aggregate of concrete, and since heavy metals are removed, It can be used as it is as concrete aggregate. As a result, it is possible to broaden the uses of the obtained steelmaking raw material.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a chlorination and volatilization step of a recycling method for using soot as an ironmaking raw material according to one embodiment of the present invention.
FIG. 2 is an explanatory diagram of a leaching step and a decarburizing step of the recycling method.
FIG. 3 is an explanatory diagram of a granulation step of the recycling method.
FIG. 4 is an explanatory diagram of a heavy metal recovery step of the recycling method.
[Explanation of symbols]
10: soot, 11: iron oxide-containing dust (iron source), 12: calcium chloride (chloride A), 13: blast furnace raw material (iron making raw material), 14: liquid, 15: extraction tank, 16: filter press, 17 : Oxidizing furnace, 18: Pamp pelletizer, 19: Processed product, 20: Conveyor dryer, 21: Rotary kiln, 22: Burner section, 23: Volatile gas, 24: Cooling tower, 25: Washing tower, 26: Dioxin removing tower, 27 : Neutralization tank, 28: lime, 29: filter press, 30: calcium chloride concentrator

Claims (9)

A predetermined amount of an iron source and chloride A are mixed with the soot generated in the refuse treatment step and heated to 700 ° C. or higher. By this heating, the non-ferrous metal contained in the soot is converted to chloride B and volatilized. And removing the soot from the soot to obtain an iron making raw material. 2. The method of claim 1, wherein the non-ferrous metal is one or more of copper, lead, and zinc. Recycling method to make. In the recycling method for using soot as an iron-making raw material according to any one of claims 1 and 2, the soot is mixed with water or water before mixing with the iron source and the chloride A. A method for recycling soot as a raw material for iron making, wherein the soot is introduced into an acidic aqueous solution and chloride C of the alkali metal in the soot is eluted and removed. The method for recycling soot as described in any one of claims 1 to 3, wherein the soot and the mixture of the iron source and the chloride A are heated in an oxidizing atmosphere. A method of recycling soot as an iron-making raw material, characterized by suppressing volatilization of iron in the iron source. In the recycling method for using soot as an iron making raw material according to any one of claims 1 to 4, the amount of iron in the iron source mixed with the soot is the total weight of the iron making raw material. A recycling method for using soot as a raw material for iron making, wherein the amount is 30% by mass or more. The recycling method for using soot as an iron-making raw material according to any one of claims 1 to 5, wherein the iron source uses iron oxide-containing dust discharged from an ironworks, and A method of recycling soot as an iron-making raw material, characterized by baking a mixture of ash and the iron oxide-containing dust to remove carbon, and then mixing the chloride A. The recycling method for recycling soot as described in any one of claims 1 to 6 as a raw material for ironmaking, wherein the soot is molten fly ash generated in a step of turning a residue generated during incineration of waste into slag. A recycling method for using soot as a raw material for ironmaking. A method for recycling soot as claimed in any one of claims 1 to 7, wherein the soot is used as a blast furnace raw material. Resource recycling method. A method for recycling soot as an iron making raw material according to any one of claims 1 to 7, wherein the soot and iron making raw material is used as an aggregate of concrete. Resource recycling method.

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